Generation of short laser pulses is important when studying various phenomena, transient and otherwise, and especially in the field of communications. Other applications are found in the field of non-linear optics; spectroscopy of liquids, gases and solids; relaxation measurements in biology; and, perhaps, in such devices as passive-ring gyroscopes.
In the past when one wished to produce a train of pulses, the accepted procedure was to fix the phases of the oscillating modes in a laser by modification of the feedback condition. One method of modifying the feedback is by modulating the gain, loss or phase of the laser cavity. Another method feeds back frequency-shifted waves into the oscillator. Current technology requires a pulsed laser to pump a dye laser. This leads to low output powers from the dye laser and generally inefficient pulse generation.
1. Field of the Invention
The present invention relates to the generation of short laser pulses within a cavity by employing a frequency shifter to shift the frequency of continuous waves passing therethrough by an incremental amount such that the sum of the frequency-shifted waves circulating or otherwise reflected within the cavity comprises a series of discrete pulses.
2. Description of the Related Art
Representative of the related art is the U.S. patent to Tang et al. U.S. Pat. No. 4,485,473 together with several of the prior art patents and literature references therein which relate to the generation of pulses in a ring cavity; however, all of these prior art references together with others known to applicant of a similar nature fall within the well known class of pulse generators which accomplish the objective through the use of one or the other of the techniques set forth previously, i.e. either by modulating the gain, loss or phase of the laser cavity or, alternatively, feeding back frequency-shifted waves into the oscillator. Applicant is unaware of any pulse-generation method, apparatus or techniques which employs a continuous wave circulating within a passive cavity, the frequency of which is shifted each pass by means of a frequency-shifting device such that the sum total of the frequency-shifted waves is such that a circulating pulse is produced.